The present invention relates, in general, to the detection of extravasation (i.e. leakage) of infusions and the like and, in particular, to optically detecting extravasation at an infusion site.
Various beneficial substances are intravascularily administered to hospital patients. Examples of these substances are fluids such as contrast media, medicinal fluids, water, electrolytes, sugar, blood, and pharmaceuticals. These substances typically are administered with a needle that is adapted to be inserted into an appropriate vein or artery.
Extravasation occurs when, during the infusion of such a substance, the substance being applied infiltrates the area around the vein or artery. For example, improper insertion of a needle or movement of the patient can cause the needle to pierce the far vascular wall so that the substance is administered into the perivascular tissue or the needle can simply withdraw from the vein or artery and inadvertently inject fluid into the surrounding tissue.
Extravasation can occur while using a variety of units that are used to inject fluids into a patient. Such units include, for example, syringes, power injectors, intravascular drips, intravascular pumps and the like.
Among the various injected substances are diagnostic contrast agents and chemotherapy substances that can be toxic or irritating to body tissue. The extravasation of such substances and others can cause serious harm to patients. Consequently, immediate and accurate detection of extravasation can be very important with such toxic substances, as well as with other injected substances. There is a particularly high risk of injury when high speed bolus injections are used with various medical imaging contrast agents.
A variety of methods for extravasation detection are known in the art.
U.S. Pat. No. 4,647,281 describes and illustrates and infiltration detection apparatus that utilizes microwave antenna means positioned over an area of infusion and a microwave radiometer for detecting sub-cutaneous temperature. Extravasation is detected by temperature differentials between injected fluids and surrounding tissues.
U.S. Pat. No. 5,334,141 describes and illustrates another system for extravasation detection that also monitors electromagnetic microwave emissions from the patient. This patent shows an antenna assembly having a reusable antenna element connected to processing apparatus and a disposable attachment element for adhering to the skin of a patient.
U.S. Pat. No. 4,877,034 describes and illustrates yet another non-invasive system that allows detection of tissue infiltration during the administration of fluids. Tissue surrounding the site of intravenous injection is exposed to a plurality of wavelengths of electromagnetic radiation when no infiltration is occurring to determine a baseline reading. Changes in the relative levels of detected radiation at each wavelength as compared to the baseline reading indicate tissue infiltration.
Another technique previously suggested involves use of an optical device that detects extravavsation and subsequently controls the injector to stop further supply of the of the contrast agent. The basic idea underlying this technique requires that, when a light emitter-detector pair is placed proximal to a catheterized vessel, the detected signal dynamics will differentiate extravasations from in vessel injections.
Extravasation detection apparatus, constructed in accordance with the present invention, includes a support pad adapted for attachment to a body part of a patient in proximity to a site at which a fluid is to be injected into the patient and a plurality of light sources, mounted to the support pad, for radiating light into the body part. Also included in this extravasation detection apparatus are means for energizing the light sources in an encoded manner to radiate light into the body part in an encoded manner. Extravasation detection apparatus, constructed in accordance with the present invention, also includes a plurality of light detectors, mounted to the support pad, for individually detecting light transmitted from the light sources that is reflected, scattered, diffused or otherwise emitted from the body part and individually developing light source/light detector pair signals representative of the light detected by the light detectors. Extravasation detection apparatus, constructed in accordance with the present invention, further includes means for developing, prior to injection of the fluid into the body part, a plurality if individual light source/light detector pair baseline signals associated with each light source/light detector pair and against which measurements made during injection of the fluid into the body part are compared and means for comparing the light source/light detector pair signals with the associated light source/light detector pair baseline signals. This extravasation detection apparatus also includes means for developing from the comparisons of the light source/light detector pair signals with the associated light source/light detector pair baseline signals new light source/light detector pair signals having an improved signal-to-noise ratio. Also included in extravasation detection apparatus constructed in accordance with the present invention are means for developing, prior to injection of the fluid into the body part, a model, dependent on the arrangement of the light sources and the light detectors on the support pad, for calculating extravasation volume from the new light source/light detector pair signals having an improved signal-to-noise ratio and means for combining, according to the extravasation model, the new light source/light detector signals having an improved signal-to-noise ratio to determine the volume of extravasation. This extravasation apparatus further includes means for comparing the volume of extravasation with a prescribed level of extravasation.
A method for detecting extravasation of a fluid applied to a patient in accordance with the present invention includes the steps of attaching a support pad to a body part of a patient in proximity to a site at which a fluid is to be injected into the patient, radiating, in an encoded manner into the body part at the site at which the fluid is injected into the patient, light from a plurality of light sources mounted to the support pad; and detecting light transmitted from the light sources that is reflected, scattered, diffused or otherwise emitted from the body part individually by a plurality of light detectors mounted to the support pad. This method also includes developing a plurality of light source/light detector pair signals representative of the light detected individually by the light detectors for each of the light sources and developing, prior to injection of the fluid into the body part, a plurality of individual light source/light detector pair baseline signals associated with each light source/ light detector pair and against which measurements made during injection of the fluid into the body part are compared. This method further includes developing from comparisons of the light source/light detector pair signals with the light source/light detector pair baseline signals new light source/light detector pair signals having an improved signal-to-noise ratio. Prior to injection of the fluid into the body part, an extravasation model, dependent on the arrangement of the light sources and the light detectors on said support pad, is developed for calculating extravasation volume from the new light source/light detector pair signals having an improved signal-to-noise ratio. This method further includes combining, according to the extravasation model, the new light source/light detector pair signals having an improved signal-to-noise ratio to determine the volume of extravasation and comparing the determined volume of extravasation with a prescribed level of extravasation.